1. Field of the Invention
The present invention relates generally to a data combining method in a mobile communication system, and in particular, to a method for selectively combining the same broadcast data received through a plurality of paths.
2. Description of the Related Art
Currently, a Code Division Multiple Access (CDMA) mobile communication system provides a voice service and a data service in which a large volume of data such as packet data and circuit data is transmitted. It is expected that in the near future, the CDMA mobile communication system will support multimedia broadcast/communication in which a multimedia service can be transmitted.
In a common mobile communication system, because radio transmission resources are limited, it is not efficient to transmit high-rate data on a point-to-point basis. For example, in order to transmit a 64-Kbps video streaming service to one user equipment (UE), radio resources necessary for transmitting 64-Kbps data should be allocated to the UE. However, if the number of UEs increases to n, the required amount of radio resource to be allocated also increases n times.
Alternatively, when a plurality of UEs desire to receive the same service, the service can be provided using the same radio resource regardless of the number of UEs located in the same cell and desire to receive the same service. This makes it possible to efficiently use the radio resource.
In order to support the multimedia broadcast/communication, research is being conducted on a broadcast service provided from several multimedia data sources to a plurality of UEs. A typical example of the broadcast service is Multimedia Broadcast/Multicast Service (MBMS) proposed in 3rd Generation Partnership Project (3GPP).
The MBMS service supports transmission of multimedia data, such as real-time image and voice, still image, text, etc., and can simultaneously provide voice data and image data with application of multimedia transmission. Therefore, the MBMS service requires a large amount of transmission resources. The MBMS service can be provided over a broadcast channel because of the possibility that a plurality of UEs will request the same MBMS service.
Generally, the MBMS service can be divided into two service types: a Point-to-Point (PtP) service and a Point-to-Multipoint (PtM) service. In the PtP service where a desired MBMS service is independently provided to each individual UE, dedicated channels should be allocated to the UEs. In the PtM service where an MBMS service is provided in common to a group of UEs requesting the same MBMS service, a common channel should be allocated to the UEs requesting the same MBMS service.
The MBMS service described above refers to the PtM service for efficiently transmitting the same data to a plurality of UEs in an asynchronous Universal Mobile Telecommunications System (UMTS) mobile communication system. The MBMS service is especially advantageous for multimedia transmission that requires a large amount of radio transmission resource. Because the MBMS service can be used for a high-speed multimedia service as well as for various other services, it is expected that applications suitable for the MBMS service will continuously increase in number in the future.
Even though the same MBMS service is provided to a plurality of UEs using a common channel in this way, the limitation on radio resource remains. According to simulations, in order to maintain a predetermined block error rate (BER) on 80 to 90% of a cell while transmitting 64-Kbps data over a common channel, 30% or more of available transmission power of the cell should be used.
The simulation result implies that the following problems should be taken into consideration.
First, in order to provide an MBMS service whose quality can be satisfied by all UEs located in the same cell, most of available transmission power of the cell should be used for one service.
Second, when available transmission power of the cell is limited, there is high possibility that UEs located in the boundary of the cell will experience quality degradation.
In order to solve these problems, there has been proposed a method in which a UE located in the boundary of the cell receives data from a plurality of cells when a particular service is simultaneously transmitted from several neighbor cells. However, only a concept thereof has been discussed, and no detailed method for realizing the concept has been presented yet.
Accordingly, there have been many demands for a detailed method for receiving data transmitted from several cells and appropriately using the data by enabling an appropriate exchange of control signals between a Node B and a UE, and mounting a new device in the UE when a particular service is simultaneously transmitted from several neighbor cells.